1. Field
Embodiments of the invention generally relate to methods for pore sealing of a damaged low-k film using a UV-assisted photochemical vapor deposition process.
2. Description of the Related Art
Semiconductor devices include metal layers that are insulated from each other by dielectric layers. As device features shrink, reducing the distance between the metal layers and between metal lines on each layer, capacitance increases. To address this problem, new insulating materials that have a relatively low dielectric constant are being used in place of silicon dioxide to form the dielectric layer that separates the metal lines. An exemplary material that may be used to form such a low-k dielectric layer is porous carbon doped oxide (CDO). Using this material instead of silicon dioxide to separate metal lines can yield a device having reduced propagation delay, cross-talk noise and power dissipation.
Porous carbon-doped oxides achieve lower dielectric constants through the incorporation of non-polar covalent bonds (e.g., from the addition of carbon) and the introduction of porosity to decrease film density. Introducing porosity or the incorporation of terminal bonds, such as Si—CH3, breaks the continuity of the rigid Si—O—Si lattice of oxides, yielding a lower dielectric constant layer that is both mechanically and chemically weaker. Because of the mechanical weakness, porous carbon-doped oxides are susceptible to process-related damages and contamination caused by plasma ashing, and other processes in the wire machining process such as a back-end-of-line (BEOL) process. The effective dielectric constant for the low-k dielectric layer rises accordingly.
Therefore, there is a need in the art for an improved method which minimizes process-related damages and seals the exposed pores prior to further processing so that the dielectric constant of the low-k film can be restored.